SOS Forests

Decline in Anthropogenic Fire (Not Fire Suppression) Responsible For Forest Changes in Finland and Canada

A recent paper [here], by Tuomo Wallenius of the Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland, puts the fire suppression theory to bed.

Wallenius, T. 2011. Major decline in fires in coniferous forests – reconstructing the phenomenon and seeking for the cause. Silva Fennica 45(1): 139–155.

Abstract:

Steep decline in forest fires about a century ago occurred in coniferous forests over large areas in North America and Fennoscandia. This poorly understood phenomenon has been explained by different factors in different regions. The objective of this study is to evaluate the validity of the four most commonly suggested causes of the decrease in forest fires: fire fighting, over-grazing, climate change and human influence. I compiled the available dendrochronological data and estimated the annually burned proportions of Pinus-dominated forests in four subcontinental regions during the past 500 years.

These data were compared to the development of fire suppression, grazing pressure, climate and human livelihoods. The annually burned proportions declined over 90% in all studied regions. In three out of the four regions fires decreased decades before fire suppression began (emph added).

Available drought data are annually well correlated with fires but could not explain the decrease of the level in annually burned areas. A rapid increase in the number of livestock occurred at the same time with the decrease in fires in the Western US but not in Fennoscandia. Hence, fire suppression in Central Fennoscandia and over-grazing in the Western US may have locally contributed to the reduction of burned areas.

More general explanation is offered by human influence hypothesis: the majority of the past forest fires were probably caused by humans and the decrease in the annually burned areas was because of a decrease in human caused fires (emph added). This is in accordance with the old written records and forest fire statistics. The decrease in annually burned areas, both in Fennoscandia and the United States coincides with an economic and cultural transition from traditional livelihoods that are associated with high fire use to modern agriculture and forestry.

Keywords: human influence, fire-history, fire suppression, forest dynamics, Pinus

See also:

Wallenius, Tuomo H., Juho Pennanen, and Philip J. Burton. 2011. Long-term decreasing trend in forest fires in northwestern Canada. Ecosphere 2:art53. [here]

Abstract:

The annual area of forest burned has decreased in recent centuries over large areas of Fennoscandia, Siberia and temperate North America. To determine if this same trend extends to a sparsely populated region of northern Canada, fire scars on living and dead trees, forest stand ages and charred wood were systematically sampled in 85 study plots in an area of 564,000 km2 in northwestern Canada. A significant negative trend in the occurrence of forest fires was observed: average area burned per year decreased from 2.0% in the first half of the 19th century to 0.33% in the later half of the 20th century. Annually burned areas correlated significantly with a local tree ring based index, July monthly drought code and the Pacific decadal oscillation but not with June-August mean temperature, distance to the nearest road, or the year of road building. None of the climatic indicators or access history (indicative of the start of local fire suppression) could explain the long-term negative trend in fires. Earlier interpretations that humans dominated the causes of forest fires in the past, even in sparsely populated regions, deserve further attention as a possible explanation for the decreasing trend in fires (emph added).

Key words: annually burned area, boreal forest, Canada, climate, fire cycle, fire suppression, forest fire, human influence

See also:

White, C.A., D.D.B. Perrakis, V.G. Kafka, and T. Ennis. 2011. Burning at the edge: integrating biophysical and eco-cultural fire processes in Canada’s parks and protected areas. Fire Ecology 7(1): 74-106 [here]

Abstract:

Currently, high intensity, large-area lightning fires that burn during droughts dominate Canada’s fire regimes. However, studies from several disciplines clearly show that humans historically ignited burns within this matrix of large fires. Two approaches for fire research and management have arisen from this pattern: a “large-fire biophysical paradigm” related to lightning-ignited fires, and an “eco-cultural paradigm” related to human-caused burning. Working at the edge between biophysically driven fires and eco-cultural burns, and their associated management and research paradigms, presents unique challenges to land managers. We proceed by describing fire frequency trends across Canada, and how an interaction between changing climatic and cultural factors may provide better causal explanations for observed patterns than either group of factors alone. We then describe four case histories of fire restoration into Canadian landscapes moving through evolution, or deliberate intent, towards increasing emphasis on an eco-cultural paradigm. We show that use of cultural burns maintains this facet of the long-term regime while providing greater capacity for larger, higher intensity fires to occur with fewer negative ecological and socio-economic implications. Key lessons learned by practitioners restoring fire to landscapes include: 1) fire is only one process in ecosystems that also include other complex interactions, and thus restoration of fire alone could have unintended consequences in some ecosystems; 2) recognizing long-term human roles of not only fire managers, but also hunters and gatherers is critical in restoration programs; and 3) this diversity of past, present, and future ecological and cultural interactions with fire can link managers to a broad constituency of stakeholders. Bringing this variety of people and interests into the decision-making processes is a necessary pre-requisite to successful fire management at the edge.